The most common types or more accurately; causes of dementia – Alzheimer’s disease, vascular dementia, dementia with Lewy bodies and frontotemporal dementia – are all progressive. This means that the structure and chemistry of the brain become increasingly damaged over time. The person’s ability to remember, understand, reason and communicate will gradually decline. As dementia worsens, the person will need more and more support with daily living. Their behaviour and mood will also change.

Health professionals often use scales to measure these changes. At different times they may assess a person’s mental ability (eg Mini Mental State Examination), daily living skills (eg dressing, managing medication), behaviours, overall functioning or quality of life. Some of these scales were developed specifically for Alzheimer’s disease and work better for that than for other types of dementia. Assessment of the extent of someone’s dementia should take account of these scales but should also take a broader view of the person, including their capabilities and needs.

Looking at dementia as a series of three stages – early, middle and late – can be a useful way of understanding the changes that occur over time. However, it is important to realise that this view of dementia can only provide a rough guide to the course of the illness. This is because:

  • some symptoms may appear earlier or later than indicated here, in a different order, or not at all
  • the stages may overlap – the person may need help with one task, but may be able to manage another activity on their own
  • some symptoms, such as irritability, may appear at one stage and then vanish, while others, such as memory loss, will worsen over time.

The way that a person experiences dementia will depend on many factors. These include their physical make-up, other illnesses they may have, their emotional resilience, the medication they take and the support they can rely on.